1. Technical Field:
The present invention relates to improvements in automated chromatography systems.
2. Discussion of the Prior Art:
Gel permeation chromatography is a well known technique for separating and retaining selected residue components from lipids, sludges, soil, etc. An automated liquid chromatography system employing gel permeation is disclosed in U.S. Pat. No. 3,744,219 (Tindle et al). In the Tindle et al system up to twenty-three individual sample loops or containers are filled with crude sample media, and each sample is sequentially injected into a gel permeation column. As an injected sample is forced through the column, the larger molecules, which are usually the unwanted components of the sample, exit from the column first and are discarded. The smaller molecules to be eluted travel through the gel pores and thereby follow a relatively long and tortuous path to exit from the column after the unwanted larger molecules which are excluded from the pores and therefore travel a more direct path through the column.
Although the Tindle et al automated system represents a significant improvement over prior manually-operated systems, it nevertheless has certain inherent disadvantages and drawbacks. For example, each sample must be loaded into a separate respective sample sizing loop. Since subsequent analysis and processing are greatly simplified if all samples have the same volume, the twenty-three loops must have volumes that are precisely matched within one percent. In addition, the process of loading samples into the respective sample loops is relatively time-consuming, particularly in the case of viscous sample fluids. Further some samples, while awaiting processing, tend to crystallize or otherwise fall out of solution in their respective loops, resulting in flow restrictions in the system flow path and/or loss of sample material. Moreover, after each loop has been filled with sample fluid by a common syringe, the flow paths, leading to the remaining loops, including the loading syringe, must be manually cleansed, thereby increasing the total time required for sample loading.
Another limitation of the Tindle et al system resides in the fact that once the system is placed in the automatic operation mode, no further samples may be added for processing. All of the samples to be processed must be loaded in sequence, starting with the first sample loop, prior to the initiation of automatic processing. Moreover, all samples must be similar in composition.
In systems of the type described herein, wherein sample fluid is transported between different locations by purge gas or other pressurized fluid, there is a tendency for sample storage containers to leak under the relatively high pressure of the purge gas. Apart from aesthetic considerations, the loss of sample fluid by leakage can result in inaccurate processing by causing variations from the standard volume in any given sample.